[Leetcode 235, Easy] Lowest Common Ancestor of a Binary Search Tree

Problem:

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.

According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”

        _______6______       /              \    ___2__          ___8__   /      \        /      \   0      _4       7       9         /  \         3   5

For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.

Analysis:

Solutions:

C++:

    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {        if(root == NULL)            return NULL;                int max_val = max(p->val, q->val);        int min_val = min(p->val, q->val);                TreeNode *p_cur = root;        while(p_cur->val <= min_val || p_cur->val >= max_val) {            if(p_cur->val == min_val || p_cur->val == max_val)                break;            if(p_cur->val < min_val)                p_cur = p_cur->right;            else                p_cur = p_cur->left;        }                return p_cur;    }

Java:

Python: